In the movie The Matrix, Mr. Smith is able to enter any body at any time and take it over. This happens when the matrix is threatened, by Neo or others.
This scenario is a reflection of the world in which we live.
For example: you are talking to a friend, an acquaintance, a familie member, a colleague and everything is fine until you say something about things like 911, corrupt governments, vaccinations that are not safe or effective, the climate hoax, freedoms disappearing etc., oftentimes something remarkable will happen ... Mr. Smith appears and replaces the person you are talking to, to attack you, because all truths threaten the matrix.
The matrix has already been programmed into most people in their youth and subsequently maintained by politicians and the media. By this Mr. Smith programming, people have become matrix guardians, protectors of the code, police of the mind control, enforcers of the brainwashing that maintains our false concept of reality and holds it together like super glue.
Our 'educators' program most of us to be like that, to attack everyone at any time when someone in the matrix dares to speak a truth and thereby disrupt the code of slave control. These Mr. Smith-like citizens appear to be 'waiting' for those who speak against the control matrix; those people who connect the dots; those people who see through the patterns in the slave code and make them known ... and then the empty and selfish souls, as they are trained to do, attack like Pavlovian dogs.
When Mr. and Mrs. Smith -'agents'- appear around you when you speak a truth and attack you - so that you do not wake up others - do not be afraid, every truth thought, every truth written, every truth spoken, is a signal to and in the matrix and causes the matrix to crumble, bit by bit.
That which the matrix fears the most is truth, hence Mr. and Mrs. Smith to suppress it. Truth is one of the most powerful weapons in the universe. Truth, given its very nature, needs no support from any system. Truth is strong and powerful enough to stand on its own. Truth is what it is; immutable. Truth is therefore invincible and will ultimately prevail, always.
So, when you 'attack' someone for no reason other than disagreeing with them; feel somehow threatened by what they say, you might have become an 'agent', whether you realise it or not.